1. Field of the Invention
The present invention relates to a resin board which is used as a circuit board, a connection medium body, a manufacturing process for a connection medium body a circuit board and a manufacturing process for a circuit board.
2. Description of the Related Art
In recent years, together with the miniaturization, reduction of weight, increased functionality and increased performance of electronic devices, the demand has become strong, concerning industrial application as well as concerning application in the broad field of consumer devices, for a multi-layer circuit board on which semiconductor chips such as LSIs can be mounted in high density at an inexpensive price.
A resin multi-layer circuit board which can be supplied less expensively than a ceramic multi-layer board and which can fulfill the above described market demand has attracted attention as a substitute for a conventional ceramic multi-layer board and technological development has been carried out to develop a resin multi-layer circuit board that is a board suitable for high density mounting.
As a resin multi-layer circuit board developed in this manner, a circuit board of an any layer inner via hole construction has been disclosed in Japanese Unexamined Patent Publication No. Hei 06-268345 (1994). This circuit board is a resin multi-layer board using a composite material of aramid non-woven fabric reinforcing material and an epoxy resin as the insulating layer and, therefore, can be supplied at a comparatively inexpensive price. In addition, this circuit board adopts the any layer inner via hole construction, that is to say, an interstitial via hole connection construction which can connect arbitrary positions in wiring layers through conductive paste and, therefore, becomes suitable for high density mounting.
A circuit board of the any layer inner via hole construction having the above characteristics cannot be formed unless a prepreg is used which has voids in the inside due to the impregnation of resin into a non-woven fabric. That is to say, this circuit board has a construction which can be implemented only by using a particular material.
However, in addition to a higher density of mounting, today, market demands have become as follows. That is to say, market demands are manifold and there are demands such as a circuit board of a low dielectric constant suitable for a high speed circuit network, a circuit board of a high heat resistance, and the like. Therefore, it is required to implement a circuit board which has characteristics that fulfill respective desires and suitable for high density mounting.
Accordingly, the main purpose of the present invention is to provide a circuit board which can implement a low connection resistance and an excellent connection stability.
In order to achieve the above described purpose, the present invention provides a compression function layer on at least one board surface to gain a resin board used in an insulating layer of a circuit board or a connection medium body. The compression function layer has characteristics such that it adds the function of being compressed by receiving pressure in the direction of the thickness to a resin board or a medium connection body.
According to the present invention, a circuit board which adds a compression function and implements a low via connection resistance and an excellent connection stability can be gained without being limited to a specific combination of materials and, rather, can be gained by making the surface have specific characteristics.
The compression function layer is preferably a porous layer. Then, by controlling the degree of invasion of a resin component of the resin board into the porous layer, the function of being compressed by receiving pressure in the direction of thickness can be added to the resin board.
The porous layer has a hole group wherein the hole group is preferably formed of a plurality of holes which are connected to each other so that both ends of the hole group have openings on both sides of the porous layer. Then, air held in the holes can be ejected to the outside through pressure in the direction of the board thickness. Thereby, it can be made easier for the resin component of the resin board to invade into the porous layer and the amount of invasion of this resin component to the porous layer can be easily controlled by adjusting the pressure.
The above described compression function layer can also be formed of a layer of insulating particles which is provided on a resin board or connection medium body in the condition protruding from the board surface. In this case, the insulating particles protruding from the board surface are pressed into the resin board by receiving pressure in the direction of the board thickness and, thereby, the compression function can be added to the resin board.
The resin board is preferably in a semi-cured condition on, at least, the surface on which the compression function layer is provided. Then, because of the semi-cured condition of the board material, advantages are gained as follows. That is to say, in the compression function layer made up of a porous layer, it becomes easier for a resin component to invade into the porous layer. In addition, in the compression function layer made up of insulating particles, it becomes easy to press insulating particles into the resin board.
The resin board is preferably provided with a protective film layer so as to be removable as an additional layer above the above described compression function layer. Thereby, during a manufacturing step for a circuit board using the resin board or the connection medium body, dust from the outside can be prevented from becoming attached to the compression function layer. In addition, the entire thickness of the resin board or the connection medium body can be adjusted through the addition or removal of a protective film layer. Thereby, it becomes possible to add a compression margin at the time when conductors provided through the resin board or the connection medium body in the direction of the thickness is compressed.
A resin board of the present invention can be manufactured as follows. That is to say, after a porous layer is provided on at least one board surface of a resin board, the above described porous layer is adhered to the above described resin board through pressure by applying pressure to the above described resin board of the degree that a resin component of the above described resin board does not invade into the holes of the above described porous layer.